The present invention relates to a method of controlling magnetic strip domains and, in particular to a method of generating, shifting, expanding, stretching, annihilating and detecting magnetic strip domains.
It is well known that, in ortho-ferrites or garnets, a portion in which the magnetizing direction is reversed locally can be produced and this portion is referred to as a magnetic domain. In particular, such a domain having a circular shape is referred to as a magnetic bubble domain and can be utilized as a high-density memory.
Although in addition to circular shaped magnetic bubble domains there have been known elongated magnetic domains referred to as "magnetic strip domains," there existed almost no means for applying such magnetic strip domains to a practical purpose. The sole application of such magnetic strip domains has been in the method of detecting magnetic bubble domain where the magnetic bubble domain to be detected is stretched into a magnetic strip domain in order to obtain a larger output.
One method of enlarging or stretching a bubble domain which has been considered as effective has been to provide Permalloy on the surface of the magnetic material in the shape of crossed I's (I) or in the shape of chevrons having increasingly larger numbers of chevron bars and to thereby progressively stretch or expand the bubble domain to a more easily detectable size. In this case, however, the surface of the magnetic material is made irregular by the presence of the Permalloy thereon. Further, in this case, the Permalloy overlay makes it difficult to provide on the surface conductive leads which may be necessary to shift and/or detect the magnetic bubble domain, because the Permalloy is conductive.
So far as the inventors know, there has been no method of maintaining a magnetic strip domain having a specific shape at a specific position in a magnetic material or controlling the magnetic strip domain in the magnetic material.
A primary object of the present invention is to provide a method of generating a magnetic strip domain at a specific position in a magnetic material and of shifting or rearranging arbitrarily.
Another object of the present invention is to provide a method of stretching or expanding a magnetic bubble domain to easily generate a magnetic strip domain or annihilating the magnetic strip domain.
A further object of the present invention is to provide a method of easily detecting not only the existence or absence of a magnetic strip domain but also the size and intensity thereof as well as the position, shape etc. thereof.